โ Scribed by John S. Barlow; George W. Frey Jr.; John B. Newman
No coin nor oath required. For personal study only.
Following a summary of present knowledge of the lightning-discharge mechanism, the expression of Bruce and Golde for the destruction of the cloud-image dipole by the discharge has been derived phenomenologically. The radiation power spectrum of a lightning discharge has been calculated for two cases, considering the radiation to arise from (a) the destruction of the cloud-image dipole and (b) the channel as a linear antenna.
The power spectrum of the waveform of a distant daytime atmospheric (daytime "tweek") characterized by a decrease in both amplitude and instantaneous frequency with time, has been obtained, assunfing exponential decay of a sinusoidal waveform whose frequency is that of the power-weighted mean frequency. This waveform power spectrum, the transformed results of the (b) analysis above (using available experimentally determined propagation data for very low frequencies), and one of Bowe's spectra of distant daytime atmospherics have been compared. There is reasonable agreement of the transformed discharge spectrum with the observed "tweek" spectra, despite the approximations of the calculations, the variations among individual discharges, and the interpolation and extrapolation of the propagation data. These results indicate a peak in the power spectra of distant daytime atmospherics at about 10 kc., in agreement with other "tweek" workers.
While the Bruce and Golde expression seems adequate for radiation analysis, a question has been raised concerning its use, except in special cases, for the near field analysis.
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